It is well known to receive a vehicle occupant or the like softly by an inflated airbag, when the vehicle occupant or the like dives into the airbag, by providing a vent hole to the airbag and allowing gas to flow out from the inside of the airbag via the vent hole.
In Japanese Unexamined Patent Application Publication No. H06-127330, an airbag is described that is constituted in a manner such that a vent hole of the airbag is closed until an occupant comes in contact with an occupant-facing face of the inflated airbag and is opened when the occupant comes in contact with the occupant-facing face of the inflated airbag and the occupant-facing face is moved backward.
In the above publication, a vent hole is provided at a distal-to-occupant side face on the opposite side of an occupant-facing face of an airbag. A slit is provided in the vicinity of the vent hole, and a strap is inserted through the slit. One end side of the strap passes through the inside of the airbag and is connected to the occupant-facing face of the airbag. And, the other end side of the strap is routed from the slit along an outer surface of the airbag so as to cross the vent hole, and joined to the outer surface of the airbag on the side opposite to the slit across the vent hole.
In the above publication, as the airbag is inflated, the strap is tensioned in accordance with separation of the occupant-facing face and the distal-to-occupant side face of the airbag. At this time, the other end side of the strap is tensioned along the outer surface of the airbag to cause the strap to overlap with the vent hole and the vent hole to be closed. The gas is thereby prevented from flowing out from the vent hole, the inside of the airbag is quickly pressurized, and the airbag promptly extends.
When an occupant comes in contact with the inflated airbag and the occupant-facing face of the airbag is moved backward, the strap is slackened, which causes the other end side of the strap to be separated from the vent hole by gas pressure in the airbag; thereby the vent hole is opened, which causes the gas to flow out from the vent hole into the outside of the airbag. As a result, the occupant is received softly by the airbag.
[Patent Document 1] Japanese Unexamined Patent Application Publication No. H06-127330